U.S. patent application number 14/075890 was filed with the patent office on 2014-08-21 for pressure type flow control system with flow monitoring, and method for detecting anomaly in fluid supply system and handling method at abnormal monitoring flow rate using the same.
This patent application is currently assigned to FUJIKIN INCORPORATED. The applicant listed for this patent is FUJIKIN INCORPORATED. Invention is credited to Ryousuke Dohi, Kaoru Hirata, Nobukazu Ikeda, Kouji Nishino, Katsuyuki Sugita.
Application Number | 20140230911 14/075890 |
Document ID | / |
Family ID | 47138948 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140230911 |
Kind Code |
A1 |
Hirata; Kaoru ; et
al. |
August 21, 2014 |
PRESSURE TYPE FLOW CONTROL SYSTEM WITH FLOW MONITORING, AND METHOD
FOR DETECTING ANOMALY IN FLUID SUPPLY SYSTEM AND HANDLING METHOD AT
ABNORMAL MONITORING FLOW RATE USING THE SAME
Abstract
A pressure type flow control system with flow monitoring
includes an inlet, a control valve including a pressure flow
control unit connected downstream of the inlet, a thermal flow
sensor connected downstream of the control valve, an orifice
installed on a fluid passage communicatively connected downstream
of the thermal flow sensor, a temperature sensor provided near the
fluid passage between the control valve and orifice, a pressure
sensor provided for the fluid passage between the control valve and
orifice, an outlet communicatively connected to the orifice, and a
control unit including a pressure type flow rate arithmetic and
control unit receiving a pressure signal from the pressure sensor
and a temperature signal from the temperature sensor, and a flow
sensor control unit to which a flow rate signal from the thermal
flow sensor is input.
Inventors: |
Hirata; Kaoru; (Osaka,
JP) ; Dohi; Ryousuke; (Osaka, JP) ; Nishino;
Kouji; (Osaka, JP) ; Ikeda; Nobukazu; (Osaka,
JP) ; Sugita; Katsuyuki; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIKIN INCORPORATED |
Osaka |
|
JP |
|
|
Assignee: |
FUJIKIN INCORPORATED
Osaka
JP
|
Family ID: |
47138948 |
Appl. No.: |
14/075890 |
Filed: |
November 8, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2012/002394 |
Apr 5, 2012 |
|
|
|
14075890 |
|
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Current U.S.
Class: |
137/10 ;
137/486 |
Current CPC
Class: |
G01F 1/6842 20130101;
G05D 7/0617 20130101; G01F 1/6965 20130101; G05D 7/0623 20130101;
G01F 25/0007 20130101; Y10T 137/7759 20150401; Y10T 137/7761
20150401; G01F 1/363 20130101; F16K 37/0083 20130101; G01F 15/005
20130101; G01F 1/36 20130101; Y10T 137/0368 20150401; G01F 5/00
20130101; G05D 7/0635 20130101; G01F 1/50 20130101 |
Class at
Publication: |
137/10 ;
137/486 |
International
Class: |
G05D 7/06 20060101
G05D007/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2011 |
JP |
2011-105265 |
Claims
1. A pressure type flow control system with flow monitoring,
comprising: (a) an inlet side passage for fluid; (b) a control
valve comprising a pressure type flow control unit that is
connected to a downstream side of the inlet side passage and a
valve drive unit; (c) a thermal type flow sensor that is connected
to a downstream side of the control valve; (d) an orifice that is
installed on a first fluid passage communicatively connected to a
downstream side of the thermal type flow sensor; (e) a temperature
sensor that is provided near the first fluid passage between the
control valve and the orifice to measure temperature of fluid in
the first fluid passage; (f) a pressure sensor that is provided for
the first fluid passage between the control valve and the orifice
to measure pressure of fluid in the first fluid passage; (g) an
outlet side passage that is communicatively connected to the
orifice; and (h) a first control unit comprising (i) a pressure
type flow rate arithmetic and control unit to which a pressure
signal from the pressure sensor and a temperature signal from the
temperature sensor are input, and the pressure type flow rate
arithmetic and control unit computes a first flow rate value Q of
fluid flowing through the orifice, and the pressure type flow rate
arithmetic and control unit outputs a control signal Pd to the
valve drive unit that brings the control valve into an opening or
closing action in a direction in which a difference between the
computed first flow rate value and a set flow rate value is
decreased; and (ii) a flow sensor control unit to which a flow rate
signal from the thermal type flow sensor is input, and the flow
sensor control unit computes a second flow rate of the fluid
flowing through the orifice according to the flow rate signal to
indicate an actual flow rate of the fluid flowing through the
orifice.
2. The pressure type flow control system with flow monitoring
according to claim 1, wherein the pressure sensor is provided
between an outlet side of the control valve and an inlet side of
the thermal type flow sensor.
3. The pressure type flow control system with flow monitoring
according to claim 1, wherein when a difference between the first
flow rate of the fluid computed by the flow sensor control unit and
the second flow rate of the fluid computed by the pressure type
flow rate arithmetic and control unit exceeds a set value, then the
first control unit performs an alarm indication.
4. The pressure type flow control system with flow monitoring
according to claim 1, wherein the control valve, the thermal type
flow sensor, the orifice, the pressure sensor, the temperature
sensor, the inlet side passage, and the outlet side passage, are
integrally assembled in one body, and the first fluid passage is
integrally formed in the one body.
5. A pressure type flow control system with flow monitoring,
comprising: (a) an inlet side passage for fluid; (b) a control
valve comprising a pressure type flow control unit that is
connected to a downstream side of the inlet side passage and a
valve drive unit; (c) a thermal type flow sensor that is connected
to a downstream side of the control valve; (d) an orifice that is
installed on a first fluid passage communicatively connected to a
downstream side of the thermal type flow sensor; (e) a temperature
sensor that is provided near the first fluid passage between the
control valve and the orifice to measure temperature of fluid in
the first fluid passage; (f) a first pressure sensor that is
provided for the first fluid passage between the control valve and
the orifice to measure pressure of fluid in the first fluid
passage; (g) an outlet side passage that is communicatively
connected to the orifice; (h) a second pressure sensor that is
provided for the outlet side passage on the downstream side of the
orifice to measure pressure of fluid on the downstream side of the
orifice; and (i) a control unit comprising (i) a pressure type flow
rate arithmetic and control unit to which pressure signals from the
first pressure sensor and the second pressure sensor and a
temperature signal from the temperature sensor are input, and the
pressure type flow rate arithmetic and control unit monitors
critical expansions conditions of fluid flowing through the orifice
and computes a first flow rate value Q of the fluid flowing through
the orifice, and the pressure type flow rate arithmetic and control
unit outputs a control signal Pd to the valve drive unit that
brings the control valve into an opening or closing action in a
direction in which a difference between the computed first flow
rate value and a set flow rate value is decreased; and (ii) a flow
sensor control unit to which a flow rate signal from the thermal
type flow sensor is input, and the flow sensor control unit
computes a second flow rate of the fluid flowing through the
orifice according to the flow rate signal to indicate an actual
flow rate of the fluid flowing through the orifice.
6. The pressure type flow control system with flow monitoring
according to claim 5, wherein the first control unit performs an
alarm indication when the fluid flowing through the orifice is out
of the critical expansion conditions.
7. The pressure type flow control system with flow monitoring
according to claim 5, wherein the control valve, the thermal type
flow sensor, the orifice, the first pressure sensor, the
temperature sensor, the inlet side passage, the outlet side
passage, and the second pressure sensor, are integrally assembled
in one body, and the first fluid passage is integrally formed in
the one body.
8. A method for detecting an anomaly for a fluid supply system that
uses a pressure type flow control system with flow monitoring,
wherein the method comprises the steps of: (a) installing a
plurality of valves on an upstream side, or on a downstream side,
or on both the upstream side and on the downstream side, of a
pressure type flow control system provided with flow monitoring in
a fluid supply system equipped with the pressure type flow control
system provided with flow monitoring; and (b) detecting anomalies
of the plurality of valves installed on the upstream side, or on
the downstream side, or on both the upstream side and on the
downstream side, of the pressure type flow control system provided
with flow monitoring, wherein the pressure type flow control system
has a pressure sensor, and the pressure type flow control system
further comprise a flow rate setting mechanism, a flow rate and
pressure indicating mechanism, and a flow rate self-diagnostic
mechanism, wherein an indicated value of pressure in the pressure
type flow control system provided with flow monitoring, or a
diagnosed value of the flow rate self-diagnostic mechanism, or both
the indicated value of pressure in the pressure type flow control
system provided with flow monitoring and the diagnosed value of the
flow rate self-diagnostic mechanism, are used to ascertain
anomalies of the plurality of valves, wherein the plurality of
valves intended for anomaly detection include a first valve of a
purge gas supply system and a second valve of a process gas supply
system that are installed on the upstream side of the pressure type
flow control system provided with flow monitoring, and a third
valve is installed in a process gas using system on the downstream
side of the pressure type flow control system provided with flow
monitoring, and a type of anomaly to be detected by the method is
an anomaly selected from the group consisting of an opening and
closing operational anomaly of a valve and a seat leakage of a
valve.
9. The method for detecting an anomaly in a fluid supply system
that uses the pressure type flow control system with flow
monitoring according to claim 8, wherein the flow rate
self-diagnostic mechanism of the pressure type flow control system
provided with flow monitoring is a mechanism configured to compare
initial set pressure drop characteristics and pressure drop
characteristics at diagnosis, in order to diagnose the opening and
closing operational anomaly, and to detect a seat leakage in the
second valve of the process gas supply system and to detect a seat
leakage in the first valve of the purge gas supply system, from a
change in the diagnosed value when a mixed gas comprising a process
gas and a purge gas flows in the pressure type flow control
system.
10. A method for detecting an anomaly in a fluid supply system that
uses a pressure type flow control system provided with flow
monitoring, wherein the method comprises the steps of: (a)
installing a plurality of valves on an upstream side, or on a
downstream side, or on both the upstream side and on the downstream
side, of a pressure type flow control system provided with flow
monitoring in a fluid supply system equipped with the pressure type
flow control system provided with flow monitoring; and (b)
detecting anomalies of the plurality of valves installed on the
upstream side, or on the downstream side, or on the upstream side
and on the downstream side, of the pressure type flow control
system provided with flow monitoring, wherein the pressure type
flow control system has a pressure sensor, and the pressure type
flow control system further comprises a flow rate setting
mechanism, a flow rate and pressure indicating mechanism, and a
flow rate self-diagnostic mechanism, wherein an indicated value of
pressure in the pressure type flow control system provided with
flow monitoring, or a diagnosed value of the flow rate
self-diagnostic mechanism, or both the indicated value of pressure
in the pressure type flow control system provided with flow
monitoring and the diagnosed value of the flow rate self-diagnostic
mechanism, are used to ascertain anomalies of the plurality of
valves, wherein the flow rate self-diagnostic mechanism is
configured to compare initial set pressure drop characteristics and
pressure drop characteristics at diagnosis in order to diagnose an
anomaly, wherein the flow rate self-diagnostic mechanism
ascertains, as compared with the pressure drop characteristics at
an initial setting, which pattern selected from the group
consisting of (I) a pressure drop that starts delaying immediately
after the diagnosis, (II) a pressure drop that starts delaying
during the process of the diagnosis, (III) a pressure drop that
starts accelerating immediately after the diagnosis, and (IV) a
first pressure at the start of the diagnosis that does not reach a
second pressure at the initial setting, corresponds to the pressure
drop characteristics at the flow rate self-diagnosis conducted by
the flow rate self-diagnostic mechanism; and (c) determining a
cause of the detected anomaly from the pattern of the pressure drop
characteristics at the flow rate self-diagnosis ascertained by the
flow rate self-diagnostic mechanism.
11. A handling method when a monitoring flow rate is abnormal in a
fluid supply system that uses a pressure type flow control system
provided with flow monitoring, wherein the handling method
comprises the steps of: (a) performing a flow rate self-diagnosis
by performing the steps of (i) installing a plurality of valves on
an upstream side, or on a downstream side, or on both the upstream
side and on the downstream side, of a pressure type flow control
system provided with flow monitoring in a fluid supply system
equipped with the pressure type flow control system provided with
flow monitoring; and (ii) detecting anomalies of the plurality of
valves installed on the upstream side, or on the downstream side,
or on the upstream side and on the downstream side, of the pressure
type flow control system provided with flow monitoring, wherein the
pressure type flow control system has a pressure sensor, and the
pressure type flow control system further comprises a flow rate
setting mechanism, a flow rate and pressure indicating mechanism,
and a flow rate self-diagnostic mechanism, wherein a diagnosed
value of the flow rate self-diagnostic mechanism, or both an
indicated value of pressure in the pressure type flow control
system provided with flow monitoring and the diagnosed value of the
flow rate self-diagnostic mechanism, are used to ascertain
anomalies of the plurality of valves, wherein the flow rate
self-diagnostic mechanism is configured to compare initial set
pressure drop characteristics and pressure drop characteristics at
diagnosis in order to diagnose an anomaly, wherein the flow rate
self-diagnostic mechanism ascertains, as compared with the pressure
drop characteristics at an initial setting, which pattern selected
from the group consisting of (I) a pressure drop that starts
delaying immediately after the diagnosis, (II) a pressure drop that
starts delaying during the process of the diagnosis, (III) a
pressure drop that starts accelerating immediately after the
diagnosis, and (IV) a first pressure at the start of the diagnosis
that does not reach a second pressure at the initial setting,
corresponds to the pressure drop characteristics at the flow rate
self-diagnosis conducted by the flow rate self-diagnostic
mechanism; and (iii) determining a cause of the detected anomaly
from the pattern of the pressure drop characteristics at the flow
rate self-diagnosis ascertained by the flow rate self-diagnostic
mechanism; (b) checking a shift in zero-point of the pressure
sensor after determining the cause of the anomaly detected from the
selected pattern of the pressure drop characteristics of the flow
rate self-diagnosis; (c) again performing another flow rate
self-diagnosis after adjusting the zero-point when a zero-point is
shifted; (d) ascertaining whether or not the determined cause of
the anomaly is an anomaly in the fluid supply system under
circumstances where there is no shift in zero-point; (e) resolving
the anomaly in the fluid supply system when the fluid supply system
is operating abnormally; and (f) ascertaining when the pressure
type flow control system with flow monitoring is operating
abnormally, and replacing the pressure type flow control system
when the pressure type flow control system is malfunctioning and
there is no anomaly in the rest of the fluid supply system.
12. A handling method when a monitoring flow rate is abnormal in a
fluid supply system that uses a pressure type flow control system
provided with flow monitoring, wherein the handling method
comprises the steps of: (a) performing a flow rate self-diagnosis
by performing the steps of (i) installing a plurality of valves on
an upstream side, or on a downstream side, or on both the upstream
side and on the downstream side, of a pressure type flow control
system provided with flow monitoring in a fluid supply system
equipped with the pressure type flow control system provided with
flow monitoring; and (ii) detecting anomalies of the plurality of
valves installed on the upstream side, or on the downstream side,
or on the upstream side and on the downstream side, of the pressure
type flow control system provided with flow monitoring, wherein the
pressure type flow control system has a pressure sensor, and the
pressure type flow control system further comprises a flow rate
setting mechanism, a flow rate and pressure indicating mechanism,
and a flow rate self-diagnostic mechanism, wherein a diagnosed
value of the flow rate self-diagnostic mechanism, or both an
indicated value of pressure in the pressure type flow control
system provided with flow monitoring and the diagnosed value of the
flow rate self-diagnostic mechanism, are used to ascertain
anomalies of the plurality of valves, wherein the flow rate
self-diagnostic mechanism is configured to compare initial set
pressure drop characteristics and pressure drop characteristics at
diagnosis in order to diagnose an anomaly, wherein the flow rate
self-diagnostic mechanism ascertains, as compared with the pressure
drop characteristics at an initial setting, which pattern selected
from the group consisting of (I) a pressure drop that starts
delaying immediately after the diagnosis, (II) a pressure drop that
starts delaying during the process of the diagnosis, (III) a
pressure drop that starts accelerating immediately after the
diagnosis, and (IV) a first pressure at the start of the diagnosis
that does not reach a second pressure at the initial setting,
corresponds to the pressure drop characteristics at the flow rate
self-diagnosis conducted by the flow rate self-diagnostic
mechanism; and (iii) determining a cause of the detected anomaly
from the pattern of the pressure drop characteristics at the flow
rate self-diagnosis ascertained by the flow rate self-diagnostic
mechanism; and (b) when a monitoring flow rate is abnormal due to a
change in diameter of an orifice of the pressure type flow control
system provided with flow monitoring, carrying out calibration for
the pressure type flow control system provided with flow monitoring
wherein the monitoring flow rate is considered as the correct flow
rate.
13. The pressure type flow control system with flow monitoring
according to claim 2, wherein when a difference between the first
flow rate of the fluid computed by the flow sensor control unit and
the second flow rate of the fluid computed by the pressure type
flow rate arithmetic and control unit exceeds a set value, then the
first control unit performs an alarm indication.
Description
[0001] This is a Continuation-in-Part application in the United
States of International Patent Application No. PCT/JP2012/002394
filed Apr. 5, 2012, which claims priority on Japanese Patent
Application No. 2011-105265, filed May 10, 2011. The entire
disclosures of the above patent applications are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an improvement in a
pressure type flow control system and, in particular, to a pressure
type flow control system with flow monitoring that is capable of
monitoring a controlled flow rate of the pressure type flow control
system in real-time operation by organically combining a thermal
type mass flow sensor with the pressure type flow control system
using an orifice, and a method for detecting an anomaly in a fluid
supply system and a handling method when a monitoring flow rate is
abnormal using the pressure type flow control system with flow
monitoring.
[0004] 2. Description of the Related Art
[0005] Conventionally, in a gas supply apparatus for a
semiconductor control device, a pressure type flow control system
FCS using an orifice has been widely used. This pressure type flow
control system FCS is, as shown in FIG. 16, composed of a control
valve CV, a temperature detector T, a pressure detector P, an
orifice OL, an arithmetic and control unit CD, and the like, and
the arithmetic and control unit CD is composed of a temperature
correction/flow rate arithmetic circuit CDa, a comparison circuit
CDb, an input-output circuit CDc, an output circuit CDd, and the
like.
[0006] Detection values from the pressure detector P and the
temperature detector T are converted into digital signals, to be
input to the temperature correction/flow rate arithmetic circuit
CDa, and a temperature correction and a flow rate computation are
carried out therein, and a computed flow rate value Qt is input to
the comparison circuit CDb. Furthermore, an input signal Qs as a
set flow rate is input from a terminal In, to be converted into a
digital value in the input-output circuit CDc, and the digital
value is thereafter input to the comparison circuit CDb, to be
compared with the computed flow rate value Qt from the temperature
correction/flow rate arithmetic circuit CDa. Then, in the case
where the set flow rate input signal Qs is higher than the computed
flow rate value Qt, a control signal Pd is output to a drive unit
of the control valve CV, and the control valve CV is driven in the
opening direction. In fact, the control valve CV is driven in the
valve-opening direction until a difference (Qs-Qt) between the set
flow rate input signal Qs and the computed flow rate value Qt
becomes zero.
[0007] The pressure type flow control system FCS itself is publicly
known as described above. Moreover, the pressure type flow control
system FCS is excellently characterized, in the case where the
relationship that P.sub.1/P.sub.2 is greater than or equal to about
2 (i.e., so-called critical expansion conditions) is maintained
between the downstream side pressure P.sub.2 of the orifice OL
(i.e., the pressure P.sub.2 on the side of the process chamber) and
the upstream side pressure P.sub.1 of the orifice OL (i.e., the
pressure P.sub.1 on the outlet side of the control valve CV), by
the flow rate Q of the gas Go flowing through the orifice OL, which
becomes Q=KP.sub.1 (however K is a constant). Thus, it is possible
to highly accurately control the flow rate Q by controlling the
pressure P.sub.1, and the controlled flow rate value hardly changes
even when the pressure of the gas Go on the upstream side of the
control valve CV is greatly changed.
[0008] However, because the conventional pressure type flow control
system FCS uses an orifice OL with a minute hole diameter, there
may be a risk that the hole diameter of the orifice OL varies over
time. As a result, there is a problem that a difference is caused
between a controlled flow rate value determined by the pressure
type flow control system FCS and a real flow rate of the gas Go
actually flowing through the pressure type flow control system FCS.
Consequently, it is necessary to frequently carry out so-called
"flow monitoring" in order to detect this difference, which may
highly influence the operating characteristics of semiconductor
manufacturing equipment and the quality of manufactured
semiconductors.
[0009] Therefore, conventionally, a flow control system that is
capable of simply monitoring whether or not flow control is
appropriately performed in real time has been developed in the
fields of thermal type mass flow control systems and pressure type
flow control systems. For example, FIG. 17 and FIG. 18 show one
example thereof, and this mass flow control system (mass flow
controller) 20 is composed of a flow passage 23, a first pressure
sensor 27a for pressure on the upstream side, an opening/closing
control valve 24, a thermal type mass flow sensor 25 that is
installed on the downstream side of the opening/closing control
valve 24, a second pressure sensor 27b that is installed on the
downstream side of the thermal type mass flow sensor 25, a throttle
unit (sonic nozzle) 26 that is installed on the downstream side of
the second pressure sensor 27b, an arithmetic and control unit 28a,
an input-output circuit 28b, and the like.
[0010] The thermal type mass flow sensor 25 has a rectifier body
25a that is inserted into the flow passage 23, a branched flow
passage 25b that is branched from the flow passage 23 so as to have
only a flow rate of F/A, and a sensor main body 25c that is
installed on the branched flow passage 25b, and outputs a flow rate
signal Sf denoting a total flow rate F. Furthermore, the throttle
unit 26 is a sonic nozzle that flows a fluid at a flow rate
corresponding to the pressure on the primary side when a pressure
difference between those on the primary side and the secondary side
is higher than or equal to a predetermined value. In addition, in
FIG. 17 and FIG. 18, reference symbols Spa and Spb are pressure
signals, reference symbols Pa and Pb are pressure, reference symbol
F is a flow rate, reference symbol Sf is a flow rate signal, and
reference symbol Cp is a valve opening degree control signal.
[0011] The arithmetic and control unit 28a employs the pressure
signals Spa and Spb from the pressure sensors 27a and 27b,
respectively, and the flow control signal Sf from the flow sensor
25, to output the valve opening degree control signal Cp as a
feedback, thereby performing feedback control of the
opening/closing valve 24. In other words, the flow rate setting
signal Fs is input to the arithmetic and control unit 28a via the
input-output circuit 28b, and the flow rate F of the fluid flowing
in the mass flow control system 20 is regulated so as to correspond
to the flow rate setting signal Fs. In detail, the arithmetic and
control unit 28a provides feed back to the opening/closing control
valve 24 by use of an output Cp (which is based on the pressure
signal Spb from the second pressure sensor 27b), to control the
opening or closing of the opening/closing control valve 24, thereby
controlling the flow rate F of the fluid flowing in the sonic
nozzle 26. Furthermore, the arithmetic and control unit 28a makes
use of measurement of the actual flowing flow rate F by use of an
output (i.e., the flow rate signal Sf) from the thermal type flow
sensor 25, in order to check the operation of the mass flow control
system 20.
[0012] Thus, in the mass flow control system 20 of the apparatus
model shown in FIG. 17 and FIG. 18, because two types of
measurement methods of pressure type flow measurement, using the
second pressure sensor 27b for performing flow control and a flow
measurement using the thermal type flow sensor 25 for monitoring a
flow rate, are incorporated in the arithmetic and control unit 28a,
it is possible to easily and reliably monitor whether or not a
fluid at a controlled flow rate (i.e., a set flow rate F.sub.S) is
actually flowing. That is, it is possible to easily and reliably
monitor whether or not there is a difference between the controlled
flow rate (the goal flow rate) and the real flow rate (the actual
flow rate), which exerts a high practical effect.
[0013] However, there remain many problems to be solved in the mass
flow control system 20 shown in FIG. 17 and FIG. 18. As a first
problem to address, the arithmetic and control unit 28a is
configured to control the opening and closing of the
opening/closing control valve 24 by use of both signals of the
output Spb from the second pressure sensor 27b and the flow rate
output Sf from the thermal type flow sensor 25, and to correct the
flow rate output Sf from the thermal type flow sensor 25 by use of
the output Spa from the first pressure sensor 27a. In other words,
the arithmetic and control unit 28a controls the opening and
closing of the opening/closing control valve 24 by use of these
three signals, namely, two pressure signals from the first pressure
sensor 27a and the second pressure sensor 27b, respectively, and a
flow rate signal from the thermal type flow sensor 25. Therefore,
there is a problem that not only is the configuration of the
arithmetic and control unit 28a complicated, but also stable flow
control characteristics and excellently high response
characteristics of the pressure type flow control system FCS are
reduced by opposite factors.
[0014] As a second problem to address, there is a problem in that
the installation position of the thermal type flow sensor 25, with
respect to the opening/closing control valve 24, is changed. That
is, in the mass flow control system 20 shown in FIG. 17 and FIG.
18, the response characteristics of the thermal type flow sensor 25
at the time of opening and closing of the opening/closing control
valve 24, and the gas replacement characteristics and the vacuuming
characteristics in the device main body, are greatly changed.
Consequently, it is difficult to downsize the mass flow control
system 20.
[0015] Furthermore, so-called "flow control" systems have been
widely used for gas supply devices, and the like, in semiconductor
manufacturing facilities as shown in, for example, FIG. 31. As
shown in FIG. 31, a purge gas supply system Y and a process gas
supply system X are connected in parallel on the upstream side of a
flow control system D, and a process gas using system C is
connected on the downstream side of the flow control system D.
Moreover, valves V.sub.1, V.sub.2, and V.sub.3 are respectively
installed along the way of the respective gas supply systems X and
Y and the gas using system C.
[0016] In addition, in the fluid supply system as shown in FIG. 31,
generally, the operating statuses of the valves V.sub.1 to V.sub.3
are periodically inspected, and this inspection work is absolutely
imperative in order to stably supply a required process gas through
the process gas using system C. Therefore, in the above-described
inspections (hereinafter called checks) for the valves V.sub.1 to
V.sub.3, usually, checks for the operating states of the respective
valves (including the operation of a valve actuator) and checks for
seat leakages of the respective valves, are carried out.
[0017] However, at the time of checks for the seat leakages of the
valve V.sub.3 of the process gas using system C, and for the valves
V.sub.1 and V.sub.2 on the upstream side of the flow control system
D, it is necessary to detach the respective valves V.sub.1, V.sub.2
and V.sub.3 from the pipe passages, so that each valve can be
checked by use of a separately provided test device. However, this
takes a lot of time and effort to perform these seat leakage checks
for the respective valves.
[0018] The problems relating to these inspections for the
respective valves are the same as those in the pressure type flow
control system with flow monitoring. That is, every time an anomaly
in monitoring flow rate is detected by a flow rate self-diagnostic
mechanism, it is necessary to detach the pressure type flow control
system with flow monitoring from the pipe passage to inspect it,
which is a problem because it takes a lot of time and effort.
CITATION LIST
Patent Document
[0019] Patent Document 1: Japanese Patent No. 4137666; and [0020]
Patent Document 2: Japanese Published Unexamined Patent Application
No. 2007-95042.
Problems to be Solved by the Invention
[0021] The present invention has been made to solve the
aforementioned problems in the mass flow control system that uses a
sonic nozzle, such as described in Japanese Patent No. 4137666
shown in FIG. 17 and FIG. 18. That is, because the opening and
closing of the opening/closing control valve 24 is controlled by
use of two types of different signals of pressure signals from the
first and second pressure sensors 27a and 27b and a flow rate
signal from the thermal type flow sensor 25, in order to solve the
problems that (i) not only is the configuration of the arithmetic
and control unit 28a complicated, but (ii) also excellently high
response characteristics and stable flow control characteristics
that the pressure type flow control system may have might be
diminished, it is unavoidable that the mass flow control system 20
grows to a large side. Consequently, the gas replacement
characteristics are deteriorated and vacuuming operations take a
long time, and the like. Thus, it is an object of the present
invention to provide a pressure type flow control system with flow
monitoring in which the flow control unit of a pressure type flow
control system FCS using an orifice, and a thermal type flow
monitoring unit using a thermal type flow sensor, are integrally
combined so as to independently carry out flow control and flow
monitoring respectively. In this way, the pressure type flow
control system with flow monitoring is able to make full use of the
excellent flow characteristics of the pressure type flow control
system, and is able to carry out flow monitoring by the thermal
type flow sensor in a real-time manner. Additionally, the pressure
type flow control system with flow monitoring is capable of
simplifying its arithmetic and control unit, improving the gas
replacement characteristics by drastically downsizing the device
main body part, and the like.
[0022] Furthermore, the present invention has been made to solve
the problem that it is necessary to detach the respective valves
from the pipe passages at the time of seat leakage checks, and the
like, for the valves installed on the upstream side and the
downstream side of the pressure type flow control system with flow
monitoring. Such detachment of the valves from the pipe passages
takes a lot of time and effort to perform seat leakage checks, and
the like, and this causes the problem that, even in the case where
an anomaly in monitoring flow rate is detected by the flow rate
self-diagnostic mechanism, which is provided in the pressure type
flow control system with flow monitoring, it is not possible to
swiftly figure out the cause of the anomaly occurrence, and to
adopt a necessary countermeasure, for example. Consequently, it is
difficult to determine whether or not when it is required to
replace the pressure type flow control system with flow monitoring
itself. Thus, it is an object of the present invention to provide a
method for detecting an anomaly in a fluid supply system, and a
handling method, when a monitoring flow rate is abnormal when using
a pressure type flow control system with flow monitoring, wherein
these methods are capable of simply and swiftly carrying out seat
leakage checks for valves, and swiftly making an accurate response
when the monitoring flow rate is abnormal.
Means for Solving the Problems
[0023] The inventors of the invention of the present application
have devised a pressure type flow control system with flow
monitoring that is first based on a pressure type flow control
system using an orifice, so as to use orifices of two
configurations as shown in the dotted frames of FIG. 6 and FIG. 7,
in order to carry out flow monitoring in real time. In FIG. 6 and
FIG. 7, reference symbol 1 denotes a pressure type flow control
system with flow monitoring, reference symbol 2 denotes a thermal
type flow sensor, reference symbol 3 denotes a control valve,
reference symbol 4 denotes a temperature sensor, reference symbol 5
denotes a pressure sensor, reference symbol 6 denotes an orifice,
reference symbol 7 denotes a control unit, reference symbol 8
denotes an inlet side flow passage, reference symbol 9 denotes an
outlet side flow passage, and reference symbol 10 denotes a fluid
passage in a device main body. As evident from the drawings, the
pressure type flow control system with flow monitoring in which the
installation positions of the thermal type flow sensor 2 and the
control valve 3 shown in FIG. 6 are exchanged, or switched,
corresponds to the pressure type flow control system with flow
monitoring illustrated in FIG. 7.
[0024] In addition, the reason that the pressure type flow control
system, using an orifice, is employed in a flow control method is
that the flow control characteristics of such a system are
advantageous, with a long record of use, and the like. Furthermore,
the reason that the thermal type flow sensor 2 is used as a sensor
for flow monitoring is mainly because of its flow rate, and its
record of use as a sensor, and the excellent characteristics it has
a flow sensor, and the result of consideration of the point that
the ease of real-time measurement, the responsiveness to a change
of gas type, the accuracy of flow rate measurement, the record of
use, and the like, are better than those of other flow rate
measurement sensors. Moreover, the reasons that the thermal type
flow sensor 2 is integrally assembled in the fluid passage 10 in
the device main body of the pressure type flow control system using
the orifice is that it is easy to carry out flow monitoring, and it
is easy to downsize the pressure type flow control system with flow
monitoring.
[0025] In other words, the pressure type flow control system 1 with
flow monitoring using an orifice, having the configurations shown
in FIG. 6 and FIG. 7, is a pressure control type flow system that
is characterized by that, for example, it is free of the influence
of a supply pressure fluctuation. Furthermore, it is possible, with
the pressure type flow control system 1 with flow monitoring using
an orifice, to sense an anomaly of the orifice by utilizing the
pressure drop characteristics on the upstream side of the orifice,
and it is possible to monitor supply pressure with the pressure
sensors built-in the device main body, and it is possible to
continuously monitor the flow rate with the thermal sensor.
[0026] On the other hand, as residual problems, first, an output
fluctuation of the thermal type flow sensor due to a change in
supply pressure may be forseen. That is, because output from the
thermal type flow sensor fluctuates due to change in supply
pressure, an error from a controlled flow rate may be caused at the
time of changing supply pressure. Therefore, a response, such as
easing the output fluctuation due to changes in supply pressure by
delaying the response characteristics of the thermal type flow
sensor, is required.
[0027] A second residual problem is directed to conditions at the
time of zero point adjustment. Generally, a zero point adjustment
is executed under vacuuming in a pressure sensor, and is executed
in the sealing state in the flow sensor. Accordingly, it is
necessary to protect these sensors so as not to execute a zero
point adjustment under wrong conditions.
[0028] A third residual problem is related to a thermal siphon
phenomenon of the thermal type flow sensor. That is, it is
necessary to determine an installing direction in advance of
mounting of the thermal type flow sensor and, as a result, it is
necessary to review an installing direction of the pressure type
flow control system with flow monitoring concurrently with the
design of a gas box.
[0029] A fourth residual problem is related to calibration of a
live gas flow rate. Generally, in flow rate measurement, an output
value of the thermal type flow sensor varies, even at the same flow
rate, according to a gas type. As a result, it is necessary to add
a system that automatically computes a conversion factor (i.e., a
CF value) of the thermal type flow sensor at the site using the
pressure type flow control system with flow monitoring.
[0030] A fifth residual problem is directed to a response when the
controlled flow rate is abnormal. In a current pressure type flow
control system, an alarm and an error in controlled flow rate, and
the like, are indicated on a display. At the same time, a system
that judges the controlled flow rate as abnormal, when an output
difference between monitored flow rates of the pressure type flow
control system and the thermal type flow sensor exceeds a
predetermined threshold value, is required.
[0031] As a result, first, the inventors of the invention of the
present application have conducted evaluation tests for various
types of characteristics with respect to the thermal type flow
sensor 2, which is newly incorporated in the respective pressure
type flow control systems with flow monitors of FIG. 6 and FIG.
7.
[0032] That is, as shown in FIG. 6 and FIG. 7, a fluid supply
source 11 formed of an N.sub.2 container, a pressure regulator 12,
a purge valve 13, and an inlet side pressure sensor 14, are
connected to the inlet side flow passage 8, and a data logger
(NR500) 15 is connected to the control unit 7. Moreover, a
characteristics evaluation system that performs vacuuming of the
outlet side flow passage 9 by using a vacuum pump 16 is configured,
and the step response characteristics of the thermal type flow
sensor 2, the monitoring flow rate accuracy, the supply pressure
fluctuating characteristics, and the repetitive reproducibility,
are evaluated by use of this characteristics evaluation system.
[0033] The above-described step response characteristics are
evaluated as response characteristics of thermal type flow sensor
outputs to step inputs set at predetermined flow rates, and output
responses, in the case where the set flow rate is changed in steps
from 100% (full scale) F. S.=1000 (sccm) to 20%, 50% and 100%, are
evaluated. Here, the abbreviation "sccm" stands for standard cubic
centimeter per minute. FIG. 8, FIG. 9 and FIG. 10 show the
measurement results of a flow rate setting input A.sub.1 of the
pressure type flow control system 1 and a flow rate output A.sub.2
at that time, a thermal type flow sensor output B.sub.1 (in the
case of FIG. 6), and a thermal type flow sensor output B.sub.2 (in
the case of FIG. 7), in the data logger 15 in the case where the
set flow rates are 20%, 50% and 100%, respectively.
[0034] As is also clear from FIG. 8 to FIG. 10, it has been
confirmed by the inventors that the outputs from the thermal type
flow sensor 2 converge within .+-.2% of the set output within about
4 seconds from the start of the setting.
[0035] The monitoring flow rate accuracy has also been measured and
evaluated as amounts of changes in thermal type flow sensor outputs
when a set value is shifted in units of S. P. (set points) from the
respective flow rate settings, and the error setting conditions are
-0.5% S. P., -1.0% S. P., -2.0% S. P., and -3.0% S. P.
[0036] As is also clear from FIG. 11 and FIG. 12, it has become
apparent that the monitoring flow rate accuracy of the thermal type
flow sensor 2 changes in units of set points (S. P.) according to
the flow rate setting.
[0037] The supply pressure fluctuating characteristics show a
fluctuating state of thermal type flow sensor outputs, in the case
where supply pressure is fluctuated while controlling at a constant
flow rate, and have been measured with a flow rate setting of 50%
and a fluctuation condition of supply pressure of 50 kPaG.
[0038] FIG. 13 shows the measurement results thereof, and it has
become apparent that, in the case where the thermal type flow
sensor 2 is set on the upstream side (primary side) of the control
valve 3 (in the case of FIG. 6), the change in flow rate output
from the thermal type flow sensor 2 due to fluctuation in supply
pressure exceeds a range of .+-.0.5% F. S./div by far. On the other
hand, in the case where the thermal type flow sensor 2 is set on
the downstream side (secondary side) of the control valve 3 (in the
case of FIG. 7), the change in flow rate output diverges within the
range of .+-.0.5% F. S./div. Consequently, the thermal type flow
sensor 2 is less likely to be influenced by a fluctuation in gas
supply pressure when the thermal type flow sensor 2 is set on the
downstream side (secondary side) of the control valve 3 (in the
case of FIG. 7).
[0039] The repetitive reproducibility has been measured as
reproducibility of the thermal type flow sensor outputs B.sub.1 and
B.sub.2 by repetitively inputting a flow rate from 0% to the set
flow rates when the set flow rate is set to 20% and 100%,
respectively.
[0040] As is also clear from FIG. 14 and FIG. 15, it has become
apparent that the repetitive reproducibility of the thermal type
flow sensor outputs is within the ranges of .+-.1% F. S. and
.+-.0.2% F. S. Thus, regular and precise reproducibility has been
shown.
[0041] In addition, the thermal type flow sensors 2, used in the
systems of FIG. 6 and FIG. 7, are sensors mounted in the FCS-T1000
series manufactured by Fujikin Incorporated. These sensors are used
widely as thermal type flow sensors for a so-called "thermal type
mass flow control system" (mass flow controller).
[0042] From the results of the respective evaluation tests (i.e.,
the step response characteristics, the monitoring flow rate
accuracy characteristics, the supply pressure fluctuating
characteristics, and the repetitive reproducibility
characteristics), on the basis of FIG. 6 and FIG. 7 with respect to
the thermal type flow sensor 2, the inventors of the invention of
the present application have found that there are no relative
merits whether the installation position of the thermal type flow
sensor 2 is on the upstream side (primary side), or on the
downstream side (secondary side) of the control valve 3, from the
viewpoint of the step response characteristics, the monitoring flow
rate accuracy characteristics, and the repetitive reproducibility
characteristics. On the other hand, the thermal type flow sensor 2
is preferably installed on the downstream side (secondary side) of
the control valve 3 of the pressure type flow control system (that
is, it preferably has the configuration of FIG. 7) from the
viewpoint of the supply pressure fluctuating characteristics, which
are better at this location.
[0043] Furthermore, the inventors have found that, in the case
where the thermal type flow sensor 2 is installed on the downstream
side (secondary side) of the control valve 3, the content volume
between the control valve 3 and the orifice 6 is increased. This
increase in content volume is responsible for deteriorating the gas
replacement characteristics, and delaying the pressure drop
characteristics (i.e., deteriorating the outgassing
characteristics), in the case of a low flow rate type pressure type
flow control system, and these points, or the like, become
problems.
SUMMARY OF THE INVENTION
[0044] The present invention has been created based on the results
of the above-described respective evaluation tests by the inventors
of the invention of the present application. Thus, in accordance
with a first embodiment of the present invention, the indispensable
constituent features of the invention include an inlet side passage
8 for fluid, a control valve 3 composing a pressure type flow
control unit 1a that is connected to a downstream side of the inlet
side passage 8, a thermal type flow sensor 2 that is connected to a
downstream side of the control valve 3, an orifice 6 that is
installed along the way of a fluid passage 10 communicatively
connected to a downstream side of the thermal type flow sensor 2, a
temperature sensor 4 that is provided near the fluid passage 10
between the control valve 3 and the orifice 6, a pressure sensor 5
that is provided for the fluid passage 10 between the control valve
3 and the orifice 6, an outlet side passage 9 that is
communicatively connected to the orifice 6, and a control unit 7
that is composed of a pressure type flow rate arithmetic and
control unit 7a to which a pressure signal from the pressure sensor
5 and a temperature signal from the temperature sensor 4 are input,
and computes a flow rate value Q of a fluid flowing through the
orifice 6, and outputs a control signal Pd for bringing the control
valve 3 into an opening or closing action in a direction in which a
difference between the computed flow rate value and a set flow rate
value is decreased, to a valve drive unit 3a, and a flow sensor
control unit 7b to which a flow rate signal 2c from the thermal
type flow sensor 2 is input, and computes a flow rate of the fluid
flowing through the orifice 6 according to the flow rate signal 2c,
to indicate the flow rate.
[0045] In accordance with a second embodiment of the present
invention, in the invention according to the first embodiment, the
pressure sensor 5 is provided between the outlet side of the
control valve 3 and the inlet side of the thermal type flow sensor
2.
[0046] In accordance with a third embodiment of the present
invention, in the invention according to the first embodiment or
the second embodiment, when the difference between the flow rate of
the fluid computed by the flow sensor control unit 7b and the flow
rate of the fluid computed by the pressure type flow rate
arithmetic and control unit 7a exceeds a set value, then a control
unit 7 performs an alarm indication.
[0047] In accordance with a fourth embodiment of the present
invention, in the invention according to the first embodiment, the
control valve 3, the thermal type flow sensor 2, the orifice 6, the
pressure sensor 5, the temperature sensor 4, the inlet side passage
8, and the outlet side passage 9, are integrally assembled in one
body, and the fluid passage 10 is integrally formed in this one
body.
[0048] In accordance with a fifth embodiment of the present
invention, the indispensable constituent features of the invention
include an inlet side passage for fluid 8, a control valve 3
composing a pressure type flow control unit 1a that is connected to
a downstream side of the inlet side passage 8, a thermal type flow
sensor 2 that is connected to a downstream side of the control
valve 3, an orifice 6 that is installed along the way of a fluid
passage 10 communicatively connected to a downstream side of the
thermal type flow sensor 2, a temperature sensor 4 that is provided
near the fluid passage 10 between the control valve 3 and the
orifice 6, a pressure sensor 5 that is provided for the fluid
passage 10 between the control valve 3 and the orifice 6, an outlet
side passage 9 that is communicatively connected to the orifice 6,
a pressure sensor 17 that is provided for the outlet side passage 9
on the downstream side of the orifice 6, and a control unit 7 that
is composed of a pressure type flow rate arithmetic and control
unit 7a to which pressure signals from the pressure sensor 5 and
the pressure sensor 17 and a temperature signal from the
temperature sensor 4 are input, and monitors critical expansion
conditions of a fluid flowing through the orifice 6 and computes a
flow rate value Q of the fluid flowing through the orifice 6, and
outputs a control signal Pd for bringing the control valve 3 into
an opening or closing action in a direction in which a difference
between the computed flow rate value and a set flow rate value is
decreased, to a valve drive unit 3a, and a flow sensor control unit
7b to which a flow rate signal 2c from the thermal type flow sensor
2 is input, and computes a flow rate of the fluid flowing through
the orifice 6 according to the flow rate signal 2c, to indicate the
flow rate.
[0049] In accordance with a sixth embodiment of the present
invention, in the fifth embodiment of the invention, the control
unit 7 performs an alarm indication when the fluid flowing through
the orifice 6 is out of the critical expansion conditions.
[0050] In accordance with a seventh embodiment of the present
invention, in the fifth embodiment of the invention, the control
valve 3, the thermal type flow sensor 2, the orifice 6, the
pressure sensor 5, the temperature sensor 4, the inlet side passage
8, the outlet side passage 9, and the pressure sensor 17, are
integrally assembled in one body.
[0051] In accordance with an eighth embodiment of the present
invention, a basic configuration of the invention includes
detecting anomalies of valves installed on the upstream side and/or
the downstream side of the pressure type flow control system with
flow monitoring in a fluid supply system equipped with a pressure
type flow control system with flow monitoring, having a pressure
sensor that is composed of a flow rate setting mechanism, a flow
rate and pressure indicating mechanism, and/or a flow rate
self-diagnostic mechanism, In this embodiment, anomalies are
detected by use of an indicated value of pressure in the pressure
type flow control system with flow monitoring, and/or a diagnosed
value of the flow rate self-diagnostic mechanism, and in which
valves intended for anomaly detection are a valve of a purge gas
supply system and a valve of a process gas supply system that are
installed on the upstream side of the pressure type flow control
system with flow monitoring, and a valve that is installed in a
process gas using system on the downstream side of the pressure
type flow control system with flow monitoring, and the type of
anomaly to be detected is an opening and closing operational
anomaly and a seat leakage of a valve.
[0052] In accordance with a ninth embodiment of the present
invention, in the eighth embodiment of the invention, the flow rate
self-diagnostic mechanism of the pressure type flow control system
with flow monitoring is a mechanism that is configured to compare
initial set pressure drop characteristics and pressure drop
characteristics at diagnosis, in order to diagnose an anomaly, and
to detect a seat leakage in the valve of the process gas supply
system or the purge gas supply system from a change in the
diagnosed value when a mixed gas of a process gas and a purge gas
flows in.
[0053] In accordance with a tenth embodiment of the present
invention, a basic configuration of the invention includes
detecting anomalies of valves installed in the pressure type flow
control system with flow monitoring, and on the upstream side
and/or the downstream side of the pressure type flow control system
with flow monitoring in a fluid supply system equipped with a
pressure type flow control system with flow monitoring, having a
pressure sensor that is composed of a flow rate setting mechanism,
a flow rate and pressure indicating mechanism, and/or a flow rate
self-diagnostic mechanism. In this embodiment, anomalies are
detected by use of an indicated value of pressure in the pressure
type flow control system with flow monitoring and/or the flow rate
self-diagnostic mechanism, wherein the flow rate self-diagnostic
mechanism of the pressure type flow control system with flow
monitoring is a mechanism that is configured to compare initial set
pressure drop characteristics and pressure drop characteristics at
diagnosis, to diagnose an anomaly, and it is judged or ascertained,
as compared with the pressure drop characteristics at the initial
setting, which pattern of (I) a pressure drop starts delaying
immediately after the diagnosis, (II) a pressure drop starts
delaying in the process of the diagnosis, (III) a pressure drop
starts accelerating immediately after the diagnosis, and (IV) the
pressure at the start of the diagnosis does not reach the pressure
at the initial setting corresponds to the pressure drop
characteristics at flow rate self-diagnosis by the flow rate
self-diagnostic mechanism, in order to determine a cause of the
detected anomaly from the judged pattern or ascertained pattern of
the pressure drop characteristics at flow rate self-diagnosis.
[0054] In accordance with an eleventh embodiment of the present
invention, performing a flow rate self-diagnosis by use of the
method for detecting an anomaly in the fluid supply system
according to the tenth embodiment, checking a shift in zero-point
of the pressure sensor after determining a cause of an anomaly
detected from a pattern of the pressure drop characteristics at
flow rate self-diagnosis, again performing a flow rate
self-diagnosis after adjusting the zero-point when the zero-point
is shifted, judging or ascertaining whether or not the determined
cause of the anomaly is an anomaly in the fluid supply system in
the case where there is no shift in the zero-point, restoring the
anomaly in the fluid supply system in the case where the fluid
supply system is abnormal, and judging or ascertaining that the
pressure type flow control system with flow monitoring itself is
abnormal, to replace the system in the case where there is no
anomaly in the fluid supply system.
[0055] In accordance with a twelfth embodiment of the present
invention, performing a flow rate self-diagnosis by use of the
method for detecting an anomaly in the fluid supply system in the
tenth embodiment of the present invention, and in the case where a
monitoring flow rate is abnormal due to a change in diameter of the
orifice of the pressure type flow control system with flow
monitoring, carrying out calibration for the pressure type flow
control system with flow monitoring so as to consider the
monitoring flow rate as correct.
Effect of the Invention
[0056] In the present invention, the pressure type flow control
system with flow monitoring is formed of the pressure type flow
control unit 1a and the thermal type flow monitoring unit 1b, and
the thermal type flow sensor 2 of the thermal type flow monitoring
unit 1b is located on the downstream side of the control valve 3,
to be organically integrated, and the control unit 7 is configured
by integrating the pressure type flow rate arithmetic and control
unit 7a that controls driving of opening and closing of the control
valve 3 of the pressure type flow control unit 1a, and the flow
sensor control unit 7b that computes a real flow rate of fluid
flowing through the orifice 6 with a flow rate signal from the
thermal type flow sensor 2, and indicates the real flow rate,
wherein the real flow rate and the flow rate signal are independent
of each other.
[0057] As a result, with the control unit 7 having a simple
configuration, it is possible to easily and precisely perform
stable pressure type flow control, and it is also possible to
continuously and precisely carry out flow monitoring by the thermal
type flow sensor 2 in real time.
[0058] Furthermore, because of the configuration in which the
thermal type flow sensor 2 is located on the downstream side of the
control valve 3, and the respective device main bodies, such as the
control valve 3 and the thermal type flow sensor 2 are integrally
assembled in one body, the internal space volumes of the device
main bodies are not considerably reduced, which does not
deteriorate the characteristics of the gas replacement
characteristics and the vacuuming characteristics. Moreover, even
when there is a fluctuation in fluid pressure on the side of the
fluid supply source, a great fluctuation is not caused in the
output characteristics of the thermal type flow sensor 2. As a
result, it is possible to perform stable flow monitoring and flow
control with respect to the fluctuation in pressure on the side of
the fluid supply source.
[0059] In the present invention, by use of the pressure type flow
control system with flow monitoring itself, which is incorporated
in the gas supply system, it is possible to extremely easily and
precisely check anomalies of opening and closing operations and
seat leakages in the valves in the gas supply system, an anomaly in
zero-point of the pressure type flow control system with flow
monitoring, and the like, without detaching the respective valves
from the pipe passages.
[0060] Furthermore, in accordance with the present invention, in
the case where a seat leakage in a valve or an operational anomaly
in a valve, or an anomaly of zero-point of the pressure type flow
control system with flow monitoring, is caused, it is possible to
precisely identify and judge or determine a cause of the anomaly
occurrence according to a pattern of the pressure drop
characteristic curve. This makes it possible to more efficiently
carry out repair and adjustment for the necessary devices, and the
like.
[0061] Moreover, in accordance with the present invention, in the
case where an anomaly in the monitoring flow rate is caused by a
change in diameter of the orifice of the pressure type flow control
system with flow monitoring, it is possible to swiftly calibrate
the pressure type flow control system with flow monitoring so as to
consider the monitoring flow rate as correct.
[0062] In addition, in accordance with the present invention,
because it is possible to detect a seat leakage anomaly, and to
automatically compute and indicate its leakage quantity within a
short time, it is possible to precisely and swiftly judge or
determine whether or not to continue to drive the devices and
apparatuses, and the like, and the influence by the occurrence of
the seat leakage. Thus, it is possible to easily determine the
necessity of replacement of the pressure type flow control system
with flow monitoring itself.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] FIG. 1 is a schematic diagram of a configuration of a
pressure type flow control system with flow monitoring utilizing an
orifice according to an embodiment of the present invention.
[0064] FIG. 2 is a schematic diagram of a configuration showing
another example of a pressure type flow control system with flow
monitoring, in accordance with another embodiment of the present
invention.
[0065] FIG. 3 is a schematic diagram of a configuration showing yet
another example of the pressure type flow control system with flow
monitoring.
[0066] FIG. 4 is an explanatory diagram of a configuration of a
thermal type flow sensor.
[0067] FIG. 5 is an explanatory diagram of the principle of
operation of the thermal type flow sensor.
[0068] FIG. 6 is a first conception diagram of the pressure type
flow control system with flow monitoring, which is conceived by the
inventors of the present application.
[0069] FIG. 7 is a second conception diagram of the pressure type
flow control system with flow monitoring, which is conceived by the
inventors of the present application.
[0070] FIG. 8 shows curves of the step response characteristics of
a thermal type flow sensor (in the case of a set flow rate of
20%).
[0071] FIG. 9 shows curves of the step response characteristics of
the thermal type flow sensor (in the case of a set flow rate of
50%).
[0072] FIG. 10 shows curves of the step response characteristics of
the thermal type flow sensor (in the case of a set flow rate of
10%).
[0073] FIG. 11 shows curves of the monitoring flow rate accuracy
characteristics of the thermal type flow sensor (in the case of a
set flow rate of 100% to 97%).
[0074] FIG. 12 shows curves of the monitoring flow rate accuracy
characteristics of the thermal type flow sensor (in the case of a
set flow rate of 20.0% to 19.4%).
[0075] FIG. 13 shows curves of the supply pressure fluctuating
characteristics of the thermal type flow sensor (in the case of a
set flow rate of 50%).
[0076] FIG. 14 shows curves of the repetitive reproducibility
characteristics of the thermal type flow sensor (in the case of a
set flow rate of 100%).
[0077] FIG. 15 shows curves of the repetitive reproducibility
characteristics of the thermal type flow sensor (in the case of a
set flow rate of 20%).
[0078] FIG. 16 is a configuration diagram of a pressure type flow
control system using an orifice.
[0079] FIG. 17 is an explanatory diagram of a configuration of a
mass flow control system according to a first embodiment disclosed
by Japanese Patent No. 4137666.
[0080] FIG. 18 is an explanatory diagram of a configuration of a
mass flow control system according to a second embodiment disclosed
by Japanese Patent No. 4137666.
[0081] FIG. 19 is a block configuration diagram showing an example
of a fluid supply system used for an embodiment of the present
invention according to a method for detecting an anomaly.
[0082] FIG. 20 is a flow diagram showing an example of a method for
detecting anomalies in valves of the fluid supply system according
to the present invention.
[0083] FIG. 21, comprised of FIG. 21A and FIG. 21B in an exploded
view over two pages to allow for legibility, shows the relationship
between types of faults, genesis phenomena, and causes of
occurrence at flow rate self-diagnosis.
[0084] FIG. 22 shows a representative example of pressure drop
characteristics as graphed in the case of insufficient supply
pressure at flow rate self-diagnosis of the pressure type flow
control system with flow monitoring.
[0085] FIG. 23(a) shows a representative example of pressure drop
characteristics as graphed in the event of a fault of a driving
mechanism of an air-operated valve on the secondary side.
[0086] FIG. 23(b) shows a representative example of pressure drop
characteristics as graphed in the case where there is a leakage
from the outside to the secondary side.
[0087] FIG. 24(a) shows a representative example of pressure drop
characteristics as graphed in the case where gas at a high flow
factor is mixed in.
[0088] FIG. 24(b) shows a representative example of pressure drop
characteristics as graphed in the case where gas at a low flow
factor is mixed in.
[0089] FIG. 25(a) shows a representative example of pressure drop
characteristics as graphed in the case where an orifice is
clogged.
[0090] FIG. 25(b) shows a representative example of pressure drop
characteristics as graphed in the case where the orifice
expands.
[0091] FIG. 26 shows a representative example of pressure drop
characteristics as graphed in the case where there is a seat
leakage in a control valve of the pressure type flow control system
with flow monitoring.
[0092] FIG. 27 shows a representative example of pressure drop
characteristics, as graphed, in the case where there is a fault of
a drive unit of the control valve of the pressure type flow control
system with flow monitoring.
[0093] FIG. 28 shows a representative example of pressure drop
characteristics as graphed at the time of zero-point fluctuation of
the pressure type flow control system with flow monitoring.
[0094] FIG. 29 shows the four types of pressure drop
characteristics, which are derived from the patterns of the
respective pressure drop characteristics of FIG. 21 to FIG. 26.
[0095] FIG. 30 is a flow diagram showing an example of a handling
method when a monitoring flow rate of the pressure type flow
control system with flow monitoring is abnormal.
[0096] FIG. 31 is a schematic block configuration diagram showing
an example of a fluid supply system equipped with a pressure type
flow control system with flow monitoring in a semiconductor
manufacturing facility.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0097] Hereinafter, an embodiment of a pressure type flow control
system with flow monitoring, according to the present invention,
will be described with reference to the drawings. In the drawings,
like parts are designated by like character references. FIG. 1 is a
schematic diagram of a configuration according to an embodiment of
a pressure type flow control system 1 with flow monitoring
according to the present invention. The pressure type flow control
system 1 with flow monitoring is composed of a pressure type flow
control unit 1a and a thermal type flow monitoring unit 1b.
[0098] Furthermore, the pressure type flow control unit 1a is
composed of a control valve 3a, a temperature sensor 4, a pressure
sensor 5, an orifice 6, and a pressure type flow rate arithmetic
and control unit 7a forming a component of a control unit 7.
[0099] Moreover, the thermal type flow monitoring unit 1b is
composed of a thermal type flow sensor 2 and a flow sensor control
unit 7b forming another component of the control unit 7.
[0100] The pressure type flow control unit 1a, as described above,
is composed of the control valve 3, the temperature sensor 4, the
pressure sensor 5, the orifice 6, the pressure type flow rate
arithmetic and control unit 7a, and the like, and a flow rate
setting signal is output from an input terminal 7a.sub.1, and a
flow rate output signal of a fluid flowing through the orifice,
which has been computed by the pressure type flow control unit 1a,
is output from an output terminal 7a.sub.2.
[0101] The pressure type flow control unit 1a itself, which uses
the orifice 6, is a publicly-known technique as evident from
Japanese Patent No. 3291161, and the like, and computes a flow rate
of fluid flowing through the orifice 6 under the critical expansion
conditions on the basis of pressure detected by the pressure
detection sensor 5, with the pressure type flow rate arithmetic and
control unit 7a, and outputs a control signal Pd proportional to a
difference between the set flow rate signal input from the input
terminal 7a.sub.1 and the computed flow rate signal outputted to a
valve drive unit 3a of the control valve 3.
[0102] Because the configurations of the pressure type flow control
unit 1a and the flow rate arithmetic and control unit 7a thereof
are substantially the same as those described in FIG. 16, detailed
descriptions thereof are here omitted. Furthermore, as a matter of
course, various types of ancillary mechanisms, such as the
publicly-known zero-point adjustment mechanism and flow rate
anomaly detection mechanism, and a gaseous species conversion
mechanism (F. F. value conversion mechanism), are provided in the
pressure type flow control unit 1a. Moreover, in FIG. 1, reference
symbol 8 denotes an inlet side passage, reference symbol 9 denotes
an outlet side passage, and reference symbol 10 denotes a fluid
passage in the device main body.
[0103] The thermal type flow monitoring unit 1b composing the
pressure type flow control system 1 with flow monitoring is
composed of the thermal type flow sensor 2 and the flow sensor
control unit 7b, and an input terminal 7b.sub.1 and an output
terminal 7b.sub.2 are respectively provided for the flow sensor
control unit 7b. Then, a setting signal within a flow rate range to
be monitored is input from the input terminal 7b.sub.1, and a
monitoring flow rate signal (i.e., a real flow rate signal)
detected by the thermal type flow sensor 2 is output from the
output terminal 7b.sub.2.
[0104] Furthermore, although not shown in FIG. 1, as a matter of
course, input and output of the monitoring flow rate signal and a
computed flow rate signal are appropriately carried out between the
flow sensor control unit 7b and the pressure type flow rate
arithmetic and control unit 7a, and a difference between them both,
and a level of the difference, may be monitored. Alternatively, a
warning may be issued in the case where the difference between both
the monitoring flow rate signal and the computed flow rate signal
exceeds a given value.
[0105] FIG. 2 shows another example of the pressure type flow
control system 1 with flow monitoring, which is configured to
detect fluid pressure between the control valve 3 and the thermal
type flow sensor 2 using the pressure sensor 5. In addition, other
configurations and operations of the pressure type flow control
system 1 with flow monitoring are completely the same as those in
the case of the embodiment illustrated by FIG. 1.
[0106] FIG. 3 shows yet another example of the pressure type flow
control system 1 with flow monitoring, in accordance with the
present invention, in which a pressure sensor 17 is separately
installed on the downstream side of the orifice 6. This embodiment
makes it possible to monitor whether or not the fluid flowing
through the orifice 6 is under the critical expansion conditions,
to issue an alarm, or to perform flow control by use of
differential pressure between the pressure sensor 5 and the
pressure sensor 17.
[0107] The thermal type flow monitoring unit 1b is composed of the
thermal type flow sensor 2 and the flow sensor control unit 7b, and
FIG. 4 and FIG. 5 show an outline of the configuration of the
thermal type flow monitoring unit 1b. That is, as shown in FIG. 4,
the thermal type flow sensor 2 has a bypass pipe group 2d (i.e., a
laminar flow element) and a sensor pipe 2e which bypasses the
bypass pipe group 2d. A gas fluid of a small quantity, compared to
the bypass pipe group 2d, is made to flow through the sensor pipe
2e at a constant ratio. Furthermore, a pair of resistance wires R1
and R4 for control, which are series-connected, are rolled around
the sensor pipe 2e to output a flow rate signal 2c indicating a
mass flow rate value that is monitored by a sensor circuit 2b
connected to the resistance wires R1 and R4.
[0108] The flow rate signal 2c is introduced into the flow sensor
control unit 7b composed of, for example, a microcomputer or the
like, to determine the real flow rate (i.e., the actual flow rate)
of a currently flowing fluid on the basis of the flow rate signal
2c.
[0109] FIG. 5 illustrates a basic structure of the sensor circuit
2b of the thermal type flow sensor 2, and the series-connected
circuits of two standard resistors R2 and R3 are connected in
parallel to the series-connection of the resistance wires R1 and R4
described above, so as to form a bridge circuit. A constant current
source is connected to this bridge circuit, and a connecting point
between the resistance wires R1 and R4, and a connecting point
between the standard resistors R2 and R3, are connected to the
input side, to provide a differential circuit, which is configured
to determine a potential difference between these two connecting
points and to output this potential difference as the flow rate
signal 2c.
[0110] In addition, because the thermal type flow sensor 2 and the
flow sensor control unit 7b themselves are publicly known devices,
detailed descriptions thereof are here omitted. Furthermore, in the
present embodiment, a sensor mounted in the FCS-T1000 series
manufactured by Fujikin Incorporated is used as the thermal type
flow monitoring unit 1b.
[0111] Next, an embodiment of the invention, pertaining to a method
for detecting an anomaly in a fluid supply system using the
pressure type flow control system 1 with flow monitoring, will be
described. Referring to FIG. 1, the pressure type flow control unit
1a of the pressure type flow control system with flow monitoring
has a configuration substantially equivalent to a conventional
pressure type flow control system FCS shown in FIG. 16, and a flow
rate setting circuit (not shown) corresponding to a flow rate
setting mechanism and a pressure indicating mechanism (not shown)
corresponding to a pressure indicating mechanism, a flow rate
output circuit (not shown) indicating a flow rate, and the like,
are provided in the pressure type flow control unit 1a.
Furthermore, a so-called flow rate self-diagnostic mechanism (not
shown) is provided in the pressure type flow control unit 1a, which
is, as will be described later, configured to compare initially set
pressure drop characteristics and pressure drop characteristics at
diagnosis, to judge or ascertain an abnormal state, and output its
judgment or determination as a result.
[0112] Moreover, a mechanism of transmitting a signal of
insufficient supply pressure is provided in the pressure type flow
control unit 1a for the case where supply pressure from the gas
supply source to the control valve 3 is insufficient. In this way,
a signal is provided to indicate when it becomes not possible to
supply a gas flow rate at the set flow rate, or when it becomes not
possible to maintain the critical expansion conditions.
[0113] FIG. 19 shows an example of a fluid supply system using the
pressure type flow control system with flow monitoring, which is an
objective to be implemented by the present invention. The fluid
supply system is composed of a purge gas supply system Y, a process
gas supply system X, the pressure type flow control system 1 with
flow monitoring, a process gas using system C, and the like.
[0114] Furthermore, at the time of using the fluid supply system,
usually, first, an inert gas such as N.sub.2 or Ar is, as a purge
gas Go, made to flow from the purge gas supply system Y to the pipe
passage 8, to the pressure type flow control system 1 with flow
monitoring, and to the pipe passage 9, and the like, to purge the
inside of the fluid supply system. Thereafter, a process gas Gp is
supplied in place of the purge gas Go, and the process gas Gp is
supplied to the process gas using system C while regulating its
flow rate to a desired flow rate in the pressure type flow control
system 1 with flow monitoring. In addition, in FIG. 19, reference
symbols V.sub.1, V.sub.2 and V.sub.3 are valves, such as automatic
opening/closing valves equipped with fluid pressure drive units and
electromotive drive units.
[0115] The valves inspected by use of the present invention are the
valves V.sub.1, V.sub.2 and V.sub.3 in FIG. 19, and the like, and
so-called seat leakages and operational anomalies in the valves
V.sub.1, V.sub.2 and V.sub.3 are inspected during preparation for
starting to supply a process gas to a process chamber E or during
preparation for stopping the supply of the process gas, or the
like, by use of the pressure type flow control system with flow
monitoring (hereinafter called the pressure type flow control unit
1a).
[0116] In more detail, the operational anomalies in the respective
valves V.sub.1, V.sub.2 and V.sub.3 are inspected in accordance
with the following steps by use of the pressure type flow control
unit 1a (i.e., the pressure type flow control system FCS).
[0117] A: Operational Anomaly in Valve V.sub.1: [0118] a. A
predetermined live gas (e.g., a process gas Gp) is made to
circulate or flow, and the gas is made to circulate or flow at a
predetermined set flow rate by the FCS. At this time, in the case
where a flow rate indicated value and a pressure indicated value
(in the pipe passage 8 and/or the pipe passage 9) of the FCS change
to 0, then there is an anomaly (malfunction) in operation of the
valve V.sub.1. [0119] b. A predetermined live gas (process gas Gp)
is made to circulate or flow in the FCS, and in the case where an
error signal of insufficient supply pressure is transmitted from
the FCS during diagnosis (hereinafter called a "flow rate
self-diagnosis for live gas") with respect to whether or not the
live gas controlled flow rate of the FCS is a predetermined flow
rate, then there is an anomaly (malfunction) in operation of the
valve V.sub.1.
[0120] B: Operational Anomaly in Valve V.sub.2: [0121] a. N.sub.2
is made to circulate as a purge gasGo, and this purge gas is made
to circulate or flow at a predetermined set flow rate by the FCS.
At this time, in the case where a flow rate indicated value and a
pressure indicated value of the FCS change to 0, then there is an
anomaly (malfunction) in operation of the valve V.sub.2. [0122] b.
A N.sub.2 gas is made to circulate or flow in the FCS, and in the
case where an error signal of insufficient supply pressure is
transmitted from the FCS during diagnosis (hereinafter called at
flow rate self-diagnosis for N.sub.2) with respect to whether or
not the N.sub.2 controlled flow rate of the FCS is a predetermined
flow rate, then there is an anomaly (malfunction) in operation of
the valve V.sub.3.
[0123] C: Operational Anomaly in Valve V.sub.3: [0124] a. In the
case where an error signal of flow rate self-diagnosis is
transmitted from the FCS, a flow rate self-diagnosis for N.sub.2 or
at flow rate self-diagnosis for live gas under the condition that
N.sub.2, or the live gas, is made to flow, then there is an anomaly
(malfunction of the valve V.sub.2) [0125] b. In the case where the
pressure output indication of the FCS does not drop to zero at the
time of vacuuming a pipe passage 9b, and the like, then there is an
anomaly (malfunction) in operation of the valve V.sub.3. [0126] c.
In the case where there is no change in the pressure indicated
value of the FCS even when the flow rate set value is appropriately
changed at the time of setting the flow rate of the FCS, then there
is an operational anomaly (malfunction) in the valve V.sub.3.
[0127] Furthermore, the seat leakages in the respective valves
V.sub.1, V.sub.2 and V.sub.3 are inspected in accordance with the
following steps by use of the FCS. [0128] A: Seat leakage in valve
V.sub.1: [0129] a. When there is a seat leakage in the valve
V.sub.1 at flow rate self-diagnosis of the FCS with N.sub.2, the
N.sub.2 flows back toward the live gas Gp side, and the live gas Gp
on the upstream side of the valve V.sub.1 becomes a mixed gas of
the N.sub.2 and the live gas Gp. Thereafter, when the flow rate
self-diagnosis for live gas of the FCS is executed, the flow rate
self-diagnosis for live gas is performed with the mixed gas, and
the diagnosed value becomes an abnormal value. Due to this
diagnosed value becoming an abnormal value, it becomes apparent
that there is a seat leakage in the valve V.sub.1.
[0130] More specifically, in the case of a flow factor F. F. of the
live gas (process gas Gp)>1, the diagnostic result is deviated
to the "-" side (minus side), and in the case of a flow factor F.
F. of the live gas (process gas Gp)<1, the diagnostic result is
deviated to the "+" side (plus side).
[0131] In addition, the flow factor F. F. is a value indicating how
many times by the standard gas (N.sub.2) that the live gas flow
rate is multiplied in the case where the orifice of the FCS, and
the pressure P.sub.1 on the upstream side of the orifice, are the
same. Thus, the value defined by F. F.=live gas flow rate/N.sub.2
flow rate (e.g., refer to Japanese Published Unexamined Patent
Application No. 2000-66732, and the like, such as equivalent U.S.
Pat. No. 6,314,992 B1 that is incorporated herein by
reference).
[0132] B. Seat leakage in valve V.sub.2. In the case where the
diagnosed value of the flow rate self-diagnosis for live gas is an
abnormal value, then a seat leakage is detected in the valve
V.sub.2. Because the N.sub.2 gas is mixed into the live gas Gp of
the pipe passage 8 on the upstream side of the FCS, and the flow
rate self-diagnosis for live gas is performed with the mixed gas in
the FCS, the diagnosed value becomes an abnormal value.
[0133] C. Seat leakage in valve V.sub.3. After the completion of
flow control by the FCS, the valve V.sub.3 is maintained in a
closed state, and the flow rate setting of the FCS is set to 0
(i.e., the flow rate is set to zero). Thereafter, when the pressure
indicated value of the FCS drops, a seat leakage is detected in the
valve V.sub.3.
[0134] By carrying out the respective operations by use of the FCS
as described above, it is possible to detect operational anomalies
and seat leakages in the valves V.sub.1, V.sub.2 and V.sub.3 by use
of the FCS in the fluid supply system having the configuration of
FIG. 19.
[0135] In addition, in the embodiment of FIG. 19, the fluid supply
system equipped with three valves is an object to which the present
invention is applied. Meanwhile, as a matter of course, the present
invention is applicable even when the number of the process gas
supply systems Y is more than one, or even when the number of the
process gas using systems C is more than one.
[0136] FIG. 20 illustrates a flow diagram in the case where
anomalies in the respective valves V.sub.1, V.sub.2 and V.sub.3 of
the fluid supply system shown in FIG. 19 are checked. In addition,
this flow diagram is premised on the presumption that there are no
external leakages (for example, leakages from joints, hoods, and
the like) other than seat leakages in valve V.sub.1 when
determining whether there is a seat leakage in valve V.sub.1. It is
also presumed that the respective valves V.sub.1, V.sub.2 and
V.sub.3, the FCS, and the pipe passages 8, 9, 9b, and the like,
have no external leakages other than seat leakages in valve
V.sub.2, and the drive units of the respective valves function
normally function when determining whether there is a seat leakage
in valve V.sub.2. It is further presumed that the FCS functions
normally, and that the V.sub.1 and V.sub.2 valves are not
simultaneously opened in any case, and the like, in FIG. 19.
[0137] First, according to the flow diagram of FIG. 20, an anomaly
check is started in Step S.sub.0. Next, in Step S.sub.1, operations
of closing the valve V.sub.1, opening to closing (switching) the
valve V.sub.2, closing the valve V.sub.3, and opening the FCS
control valve are carried out, and the pipe passage 9 on the
downstream side of the FCS is filled with N.sub.2.
[0138] In Step S.sub.2, the pressure indication P.sub.1 of the FCS,
i.e., the pressure indication P.sub.1 of the pressure sensor 1a in
FIG. 1 is checked, to judge or ascertain whether or not an increase
and decrease .DELTA.P.sub.1 of P.sub.1 is 0.
[0139] In the case where the .DELTA.P.sub.1 is not 0, and the
P.sub.1 rises, it is judged or determined that one or both of the
valves V.sub.1 and V.sub.2 are abnormal (e.g., have seat leakages
or operational defects). Furthermore, in the case where the
.DELTA.P.sub.1 is not 0 and the P.sub.1 is decreased, it is judged
or determined that the valve V.sub.3 is abnormal (i.e., valve
V.sub.3 has a seat leakage or an operational defect) (Step
S.sub.3).
[0140] Next, in Step S.sub.4, after vacuuming the insides of the
pipe passages by closing the valve V.sub.1, closing the valve
V.sub.2, opening the valve V.sub.3, and opening the FCS control
valve, the process gas (live gas) Gp is made to flow in the FCS by
opening the valve V.sub.1 and closing the valve V.sub.2, and the
pressure indication P.sub.1 of the FCS is checked in Step S.sub.5.
It is judged or determined that the operation of valve V.sub.1 is
normal when the P.sub.1 rises (Step S.sub.7), and it is judged or
determined that the valve V.sub.1 is abnormal in operation when the
P.sub.1 does not rise (Step S.sub.6), in order to check the
operating status of the valve V.sub.1.
[0141] Thereafter, in Step S.sub.8, after vacuuming the insides of
the pipe passages by closing the valve V.sub.1, closing the valve
V.sub.2, opening the valve V.sub.3, and opening the FCS control
valve, wherein the pressure indication P.sub.1 of the FCS is
checked by closing the valve V.sub.1 and opening the valve V.sub.2
(Step S.sub.9). It is judged or ascertained that valve V.sub.2 is
abnormal in operation when the P.sub.1 does not rise (Step
S.sub.10), in order to check the operating status of the valve
V.sub.2. Further, it is judged or ascertained that the operation of
the valve V.sub.2 is normal when the P.sub.1 rises (Step
S.sub.11).
[0142] Next, in Step S.sub.12, it is judged or determined whether
or not the anomalies in the valves in the Step S.sub.2 correspond
to an anomaly in operation of the valve V.sub.3. That is, it is
judged or determined that valve V.sub.3 is abnormal in operation
when the judgment or determination in Step S.sub.2 is "No" (i.e.,
any one of the valves V.sub.1, V.sub.2 and V.sub.3 is abnormal in
operation) and the operations of the valves V.sub.1 and V.sub.2 are
normal (Step S.sub.13). Furthermore, it is judged or determined
that the operations of the respective valves V.sub.1, V.sub.2 and
V.sub.3 are normal when the judgment or determination in Step
S.sub.2 is "Yes" (Step S.sub.14).
[0143] Next, the check for seat leakages in the respective valves
V.sub.1, V.sub.2 and V.sub.3 is carried out. That is, in Step
S.sub.15, after vacuuming the insides of the pipe passages by
closing the valve V.sub.1, closing the valve V.sub.2, opening the
valve V.sub.3, and opening the control valve 3 of the FCS, by
closing the valve V.sub.1, opening to closing (switching) the valve
V.sub.2, and closing the valve V.sub.3 in the same way as in Step
S.sub.1, the pipe passage 9b between the FCS and the valve V.sub.3
is pressurized so as to keep the pressure indication P.sub.1 of the
FCS (that is, keep the pressure between the control valve 3 and the
valve V.sub.3).
[0144] In Step S.sub.16, decompression of the P.sub.1 is checked,
and when there is decompression, it is judged or ascertained that
there is a seat leakage in the valve V.sub.3 (Step S.sub.17).
Furthermore, when there is no decompression, it is judged or
determined that there is no seat leakage in the valve V.sub.3 (Step
S.sub.18).
[0145] Next, in Step S.sub.19, after vacuuming the insides of the
pipe passages by closing the valve V.sub.1, closing the valve
V.sub.2, opening the valve V.sub.3, and opening the control valve 3
of the FCS, the pipe passages 8, 9 and 9b are decompressed
(vacuumed) by closing the valve V.sub.1, closing the valve V.sub.2,
and opening the valve V.sub.3, and thereafter the valve V.sub.3 is
closed (Step S.sub.20). Thereafter, the pressure indication P.sub.1
of the FCS is checked in Step S.sub.21, and when the pressure
indication P.sub.1 is not increased in pressure, it is judged or
determined that there is no seat leakage in the valves V.sub.1 and
V.sub.2 in Step S.sub.22, and the anomaly check is completed (Step
S.sub.31).
[0146] Furthermore, when the pressure indication P.sub.1 is
increased in pressure in Step S.sub.21, it is judged that there is
a seat leakage in one of the valves V.sub.1 and V.sub.2 (Step
S.sub.23), and the algorithm or flow diagram proceeds to the
process of judging or determining in which valve there is a seat
leakage.
[0147] In Step S.sub.24, after vacuuming the insides of the pipe
passages by closing the valve V.sub.1, closing the valve V.sub.2,
opening the valve V.sub.3, and opening the control valve 3 of the
FCS, by opening the valve V.sub.1 and closing the valve V.sub.2, a
flow rate self-diagnosis for live gas of the pressure type flow
control system 1 with flow monitoring is carried out. That is, the
pressure drop characteristics when the live gas (process gas Gp) is
made to flow and the initial set pressure drop characteristics are
compared, and when a difference between the pressure drop
characteristics and the initial set pressure drop characteristics
is an allowable value or lower, it is judged or ascertained that
there is no anomaly in the diagnosed value. Furthermore, in
contrast, in the case where the difference between the pressure
drop characteristics and the initial set pressure drop
characteristics is higher than the allowable value, it is judged or
ascertained that there is an anomaly in the diagnosed value.
[0148] In Step S.sub.24, when there is no anomaly in the diagnosed
value, it is judged or ascertained that there is a seat leakage
only in the valve V.sub.1 (Step S.sub.26). This is because, even
when there is a seat leakage in the valve V.sub.1, when there is no
seat leakage in the valve V.sub.2, a fluid flowing into the
pressure type flow control system 1 with flow monitoring (FCS) is
only the process gas Gp. Accordingly, no anomaly is caused in the
diagnosed value of the flow rate self-diagnosis for live gas.
[0149] On the other hand, in the case where there is an anomaly in
the diagnosed value in Step S.sub.24, the valve V.sub.1 is closed
and the valve V.sub.2 is opened, to carry out a flow rate
self-diagnosis for N.sub.2 of the pressure type flow control system
1 with flow monitoring in Step S.sub.27. That is, the pressure drop
characteristics when the N.sub.2 gas is made to flow and the
initial pressure drop characteristics are compared, and when a
difference between both the pressure drop characteristics when the
N.sub.2 gas is made to flow and the initial pressure drop
characteristics is an allowable value or lower, it is diagnosed
that there is no anomaly in the diagnosed value. Furthermore, in
the case where the difference between both the pressure drop
characteristics when the N.sub.2 gas is made to flow and the
initial pressure drop characteristics is higher than the allowable
value, it is diagnosed that the diagnosed value is abnormal.
[0150] In Step S.sub.28, when there is no anomaly in the diagnosed
value of the flow rate self-diagnosis for N.sub.2, it is judged or
ascertained that there is a seat leakage only in the valve V.sub.2
in Step S.sub.29. This is because, when there is a seat leakage in
the valve V.sub.1, the live gas is mixed into the N.sub.2, so as to
cause an anomaly in the diagnosed value of the flow rate
self-diagnosis for the FCS.
[0151] In contrast, in Step S.sub.28, in the case where there is an
anomaly in the diagnosed value of the flow rate self-diagnosis for
N.sub.2, a seat leakage is present in the valve V.sub.1, and a
mixed gas of the N.sub.2 and the live gas flows into the FCS, so as
to cause an anomaly in the diagnosed value. Consequently, in Step
S.sub.303 it is judged or determined that seat leakages are caused
in both of the valves V.sub.1 and V.sub.2.
[0152] In addition, in the anomaly check flow diagram of FIG. 20,
there is a flow of the algorithm in that, after detecting anomalies
in the valves V.sub.1, V.sub.2 and V.sub.3 in Step S.sub.3,
operational anomalies and seat leakage anomalies in the respective
valves V.sub.1, V.sub.2 and V.sub.3 are sequentially checked.
However, when an anomaly is detected in Step S.sub.3, it may be
first determined whether the type of the anomaly is an operational
anomaly or a seat leakage in a valve from a fluctuation level of
the anomaly, and when the type of the anomaly is an operational
anomaly, Step S.sub.4 to Step S.sub.13 may be executed. And, when
the type of the anomaly is a seat leakage anomaly, Step S.sub.15 to
Step S.sub.30 may be executed, respectively.
[0153] Furthermore, with respect to the determination of the
operational anomaly, it is possible to judge or ascertain from the
pace of increase in the pressure indication P.sub.1 or the pace of
decrease in the pressure indication P.sub.1 in Step S.sub.3. When
the pace of increase in the pressure indication P.sub.1 is high, it
is possible to judge or ascertain an anomaly in opening/closing of
the valve, and when the pace of increase in the pressure indication
P.sub.1 is low, it is possible to judge or ascertain a seat leakage
anomaly in the valve.
[0154] Next, the relationship between the pressure drop
characteristics at flow rate self-diagnosis and a cause of anomaly,
and the like, in the case where a result of the flow rate
self-diagnosis is judged or ascertained as abnormal has been
verified. In addition, the flow rate self-diagnosis is, as
described above, used to compare the initial set pressure drop
characteristics and the pressure drop characteristics at diagnosis,
and to judge or determine as abnormal in the case where a
difference between the initial set pressure drop characteristics
and the pressure drop characteristics at diagnosis is out of a
range determined in advance.
[0155] First, the inventors configured a basic fluid supply system
as shown in FIG. 19, and caused a fault (i.e., an anomaly) in a
simulating manner, and then surveyed the pressure drop
characteristics associated with the respective anomalies.
Furthermore, the inventors analyzed the relationship between the
obtained pressure drop characteristics and its occurrence factors
in order to find the existence of a close constant relationship
between the pattern of pressure drop characteristics and the
corresponding cause of the anomaly occurrence. In other words, the
inventors found, via simulations, that it is possible to know the
cause of an anomaly occurrence if a pattern of pressure drop
characteristics at the time of the anomaly occurrence becomes
apparent.
[0156] FIG. 21, comprised of FIG. 21A and FIG. 21B in an exploded
view over two pages to allow for legibility, shows that the
relationships between various specific types of faults A
(identification of faults), which are caused in a simulated manner
at flow rate self-diagnosis, and phenomena B that are caused by the
faults A, and general factors C pertaining to the faults that
directly lead to the genesis of phenomena B, may be surveyed. FIG.
21 constitutes a compilation of these relationships as a chart.
Furthermore, the numerical values 1 to 4 in the fields regarding
the patterns of pressure drop characteristics indicate the types of
the patterns of the pressure drop characteristics that are
respectively caused with respect to the specific types of faults A,
as will be described later.
[0157] FIG. 22 to FIG. 28 show the pressure drop characteristics at
flow rate self-diagnosis corresponding to cases where the
respective specific faults shown in FIG. 21 are caused and,
respectively, the horizontal axis shows the time, and the vertical
axis shows the detection pressures of the pressure type flow
control unit 1a, i.e., the FCS. That is, in FIG. 22, the control
pressure is insufficient at the time of maintaining a flow rate of
100%, due to insufficient supply pressure from the gas supply
source side, and the pattern of pressure drop characteristics
becomes a pattern of the type 4, which will be described later.
[0158] In FIG. 23(a), the pressure on the secondary side of the
orifice rises because of a fault pertaining to air operation of the
air operated valve V.sub.3 on the secondary side (i.e., the output
side of the FCS). As a result, a pressure drop delays in the
process of diagnosis (and becomes a pattern of Type 2).
Furthermore, in FIG. 23(b), the pressure on the secondary side of
the orifice rises because a leaked gas flows into the secondary
side from the outside on the secondary side of the orifice. Thus,
the pattern of the pressure drop characteristics becomes the
pattern of Type 2, which is the same pattern as that in the case of
FIG. 23(a).
[0159] In FIG. 24(a), because gas at a high flow factor (F. F.)
flows into the primary side of the pressure type control unit 1a,
i.e., the FCS, it becomes easy to increasingly outgas from a
throttle mechanism (orifice), as a result, a pressure drop in the
pressure drop characteristics accelerates (thereby exhibiting a
pattern of Type 3). In contrast, in FIG. 24(b), because gas at a
low flow factor (F. F.) flows into the primary side of the FCS, it
becomes difficult to outgas from the throttle mechanism (orifice),
and a pressure drop in the pressure drop characteristics delays
(thereby exhibiting the pattern of Type 1). In addition, the
throttle mechanism is explained with the orifice in the following
description.
[0160] In FIG. 25(a), because the orifice is clogged, it becomes
difficult to outgas from the orifice, and a pressure drop in the
pressure drop characteristics delays (thereby exhibiting the
pattern of Type 1). In contrast, in FIG. 25(b), because the orifice
is expanded in diameter (e.g., such as may occur due to flow
erosion of the opening of the orifice due to the flow of gas
through the orifice), it becomes easy to outgas from the orifice,
and a pressure drop accelerates (thereby exhibiting the pattern of
Type 3).
[0161] In FIG. 26, because a seat leakage is caused in the control
valve 3, gas flows from the control valve 3 during a flow rate
self-diagnosis, and the pressure drop in the pressure drop
characteristics delays (thereby exhibiting the pattern of Type
1).
[0162] In FIG. 27, because there is an anomaly in a transmission
system of the drive unit of the control valve 3, the control valve
does not open smoothly. Consequently, a seat leakage occurs. As a
result, supply of gas is not carried out and the gas does not flow,
therefore, the pressure drop characteristics are not changed (thus,
the pattern of Type 4 is exhibited).
[0163] FIG. 28 shows the case where the zero-point adjustment of
the pressure type flow control unit 1a goes out of order. When the
zero-point is fluctuated on the plus side, the pressure drop delays
so the pattern of Type 1 is exhibited. Furthermore, when the
zero-point is fluctuated on the minus side, the pressure drop
accelerates, and the pressure drop characteristics thereof become
those of the pattern of Type 3. Thus, in accordance with this
disclosure, a zero-point fluctuation on the side of "plus"
corresponds to pressure drop delays, and a zero-point fluctuation
of the side of "minus" corresponds to pressure drop acceleration.
Moreover, a minus fluctuation of the zero-point and a plus
fluctuation of the zero-point are phenomena that can cause problems
in any device such as a pressure sensor, a control unit 1a, and a
monitoring unit 1b.
[0164] FIG. 29 collectively shows the various patterns of the
different types of the pressure drop characteristics exhibited at
the flow rate self-diagnosis as shown in FIG. 22 to FIG. 28.
[0165] Thus, in accordance with the present disclosure, the
pressure drop characteristics are roughly classified into patterns
of four types, which are summarized below according to the
following Types 1 to 4.
[0166] Pressure drop characteristics of Type 1 (Pressure drop
delays immediately after diagnosis): This pattern is caused in the
case of a fault, such as interfusion of gas at a low flow factor,
product adhesion/dust clogging of the orifice, dust jamming in the
control valve, product adhesion (seat leakage), or a plus
fluctuation of the zero-point.
[0167] Pressure drop characteristics of Type 2 (Pressure drop
delays in the process of diagnosis): This pattern is caused in the
case of a fault of the air-operated mechanism of the valve on the
secondary side, or due to a fault of a leakage from the outside to
the secondary side, or the like.
[0168] Pressure drop characteristics of Type 3 (Pressure drop
accelerates immediately after diagnosis): This pattern is caused in
the case of a fault, such as interfusion of gas at a high flow
factor, inappropriate input of zero-point, clogging of the hole
(orifice) due to corrosion, breakage of an orifice plate, or a
minus fluctuation of the zero-point.
[0169] Pressure drop characteristics of Type 4 (The flow rate does
not reach 100% at initial diagnosis): This pattern is caused in the
case of insufficient supply pressure, a fault of the air-operated
mechanism on the primary side, dust clogging (of a prefilter), an
anomaly in the transmission system of the drive unit of the control
valve (i.e., a fault of the control valve), or the like.
[0170] As is clear from the descriptions of FIG. 21 and FIG. 22 to
FIG. 29, in accordance with the present invention, by reviewing
which one of the Types 1 to 4 a pattern of pressure drop
characteristics occurring at a flow rate self-diagnosis corresponds
to, it is possible to easily determine the cause of the fault and
its place of occurrence, which makes it possible to efficiently and
swiftly repair (or inspect) the gas supply system.
[0171] Next, when a seat leakage, or the like, is caused in a valve
of the fluid supply system, or some fault is caused in the pressure
type flow control system 1 itself, provided with flow monitoring 1,
it becomes apparent that there is an anomaly in a monitoring flow
rate occurring at the flow rate self-diagnosis. Thus, it is
determined, in accordance with the present invention, whether the
anomaly in the monitoring flow rate is caused by an anomaly in the
fluid supply system, or by an anomaly in the pressure type flow
control system 1 itself. When a fault, or the like, in the pressure
type flow control system 1 is the cause of the anomaly in the
monitoring flow rate, it is necessary to swiftly replace the
pressure type flow control system 1.
[0172] Therefore, in accordance with the present invention, when an
anomaly in monitoring flow rate appears, first, as shown by the
algorithm diagram of FIG. 30, a flow rate self-diagnosis of the
pressure type flow control system 1 with flow monitoring is
performed (Step 40). In addition, the method of flow rate
self-diagnosis is the same as the method described by FIG. 20, and
the like. Furthermore, it has become apparent that the anomaly in
monitoring flow rate is generally caused by such anomalies as a
shift in zero-point of the thermal type flow monitoring unit 1b
shown in FIG. 1, a shift in zero-point of the pressure type flow
control unit 1a, an anomaly in the fluid supply system, a fault of
the pressure type flow control system 1 itself that is provided
with flow monitoring, and the like.
[0173] A flow rate self-diagnosis is performed in Step 40 and a
result thereof is diagnosed in Step 41, and when the result of the
flow rate self-diagnosis is within a normal range determined in
advance (i.e., OK), a zero-point adjustment of the thermal type
flow sensor 2 is carried out in Step 42. Thereafter, a monitoring
flow rate output is again checked in Step 43, and when the output
of the flow rate is within the normal range determined in advance
in Step 44, this is judged as usable (i.e., OK), which is
continuously provided for use.
[0174] When the result of the flow rate self-diagnosis is out of
the set range in Step 41 (i.e., a not good or "NG" determination is
made), a cause of the anomaly in monitoring flow rate in the flow
rate self-diagnosis is analyzed in Step 45, in order to understand
and ascertain the cause of the anomaly in the monitoring flow
rate.
[0175] The factorial analysis of the anomaly of the flow rate
self-diagnosis is carried out is Step 45 according to the
descriptions of FIG. 21 to FIG. 29, and it is judged or determined
which type of the four types, Types 1 to 4, corresponds to the
cause of the anomaly.
[0176] Furthermore, in the flow rate self-diagnosis of the pressure
type flow control system with flow monitoring, in the case where it
is judged or ascertained that the cause of the anomaly in flow rate
is caused by a change in bore of the orifice according to a pattern
of the pressure drop characteristic curve (i.e., in the case of
Type 1 of FIG. 25(a) and Type 2 of FIG. 25(b)), an output value of
the flow rate from the pressure type flow control system with flow
monitoring may be calibrated so as to consider the monitoring flow
rate as the correct value (i.e., the actual flow rate as determined
by flow rate measurement). In addition, as a calibration method for
the output value of the flow rate from the pressure type flow
control system provided with flow monitoring, for example, a method
for appropriately selecting about 5 to 10 points as flow rate
detecting points is employed, in order to perform calibration by
use of differences between the corresponding monitoring flow rate
values at these respective points and the flow rate output
value.
[0177] Next, first in Step 46, it is checked as to whether or not
there is a shift in the zero-point of the pressure sensor, and when
there is no shift in the zero-point of the pressure sensor, it is
checked whether or not this corresponds to an anomaly in the fluid
supply system in Step 47. In contrast, when it becomes apparent
that there is a shift in the zero-point of the pressure sensor in
Step 46, the zero-point of the pressure sensor is adjusted in Step
48 and, thereafter, the processing is again returned to Step 40, in
order to execute another flow rate self-diagnosis.
[0178] In Step 47, is checked whether or not the cause of the
anomaly corresponds to the anomaly in the fluid supply system, and
in the case where this does not correspond to an anomaly in the
fluid supply system, it is judged or determined that there is a
cause of the anomaly in the monitoring flow rate in the pressure
type flow control system itself that is provided with flow
monitoring. When this judgment or determination is made, then
handling of replacement and/or exchange of the pressure type flow
control system with flow monitoring with a new pressure type flow
control system with flow monitoring is carried out. Furthermore, in
Step 47, in the case where it becomes apparent that the cause of
the anomaly corresponds to an anomaly in the fluid supply system in
Step 47, the fluid supply system is repaired or restored in Step
49, and, thereafter, the processing is again returned to Step 40,
to execute another flow rate self-diagnosis.
INDUSTRIAL APPLICABILITY
[0179] The present invention is widely applicable not only to gas
supplying facilities for semiconductor manufacturing equipment, but
also generally to fluid supply facilities using pressure type flow
control systems provided with flow monitors having pressure sensors
in the chemical industry, the food industry, and the like. Thus,
while making full use of the excellent flow control characteristics
of a pressure type flow control system using an orifice, and with
simple addition, it is possible to easily and precisely, and
appropriately monitor a real flow rate of a controlled fluid in
real time, and it is possible to precisely judge or ascertain, as a
result of a flow rate self-diagnosis, whether an anomaly in the
pressure type flow control system provided with flow monitoring is
caused by the pressure type flow control system itself in order to
conduct appropriate swift handling of the anomaly when a monitoring
flow rate is abnormal. Thus, in accordance with the present
invention, when broadly construed, a pressure type flow control
system provided with flow monitoring is constructed to include an
inlet side passage 8 for fluid, a control valve 3 comprising a
pressure type flow control unit 1a that is connected to a
downstream side of the inlet side passage 8, a thermal type flow
sensor 2 that is connected to a downstream side of the control
valve 3, an orifice 6 that is installed along the way of a fluid
passage 10 communicatively connected to a downstream side of the
thermal type flow sensor 2, a temperature sensor 4 that is provided
near the fluid passage 10 between the control valve 3 and the
orifice 6, a pressure sensor 5 that is provided for the fluid
passage 10 between the control valve 3 and the orifice 6, an outlet
side passage 9 that is communicatively connected to the orifice 6,
and a control unit 7 that is comprised of a pressure type flow rate
arithmetic and control unit 7a to which a pressure signal from the
pressure sensor 5 and a temperature signal from the temperature
sensor 4 are input, and computes a flow rate value Q of a fluid
flowing through the orifice 6, and outputs a control signal Pd to a
valve drive unit 3a for bringing the control valve 3 into an
opening or closing action in a direction in which a difference
between the computed flow rate value and a set flow rate value is
decreased, and a flow sensor control unit 7b to which a flow rate
signal 2c from the thermal type flow sensor 2 is input, and
computes a flow rate of the fluid flowing through the orifice 6
according to the flow rate signal 2c, to indicate the actual flow
rate.
DESCRIPTION OF REFERENCE SYMBOLS
[0180] 1: Pressure type flow control system with flow monitoring
[0181] 1a: Pressure type flow control unit [0182] 1b: Thermal type
flow monitoring unit [0183] 2: Thermal type flow sensor [0184] 2b:
Sensor circuit [0185] 2d: Bypass pipe group [0186] 2e: Sensor pipe
[0187] 3: Control valve [0188] 3a: Valve drive unit [0189] 4:
Temperature sensor [0190] 5: Pressure sensor [0191] 6: Orifice
[0192] 7: Control unit [0193] 7a: Pressure type flow rate
arithmetic and control unit [0194] 7b: Flow sensor control unit
[0195] 7a.sub.1: Input terminal [0196] 7a.sub.2: Output terminal
[0197] 7b.sub.1: Input terminal [0198] 7b.sub.2: Output terminal
[0199] 8: Inlet side passage [0200] 9: Outlet side passage [0201]
10: Fluid passage in device main body [0202] 11: Gas supply source
[0203] 12: Pressure regulator [0204] 13: Purge valve [0205] 14:
Input side pressure sensor [0206] 15: Data logger [0207] 16: Vacuum
pump [0208] 17: Pressure sensor [0209] Pd: Control valve control
signal [0210] Pc: Flow rate signal [0211] A.sub.1: Flow rate
setting input [0212] A.sub.2: Flow rate output of pressure type
flow control system [0213] B.sub.1: Output from thermal type flow
sensor (FIG. 6: In the case of thermal type flow sensor on the
primary side) [0214] B.sub.2: Output from thermal type flow sensor
(FIG. 7: In the case of thermal type flow sensor on the secondary
side) [0215] X: Process gas supply system [0216] X.sub.1: Pipe
[0217] Y: Purge gas supply system [0218] Y.sub.1: Pipe [0219] C:
Process gas using system [0220] E: Process chamber [0221] FCS:
Pressure type flow control system [0222] V.sub.1 to V.sub.3: Valve
[0223] Go: Purge gas [0224] Gp: Process gas
* * * * *